The present invention relates generally to MEMS gyroscopes, and more particularly, relates to a noise source for starting a MEMS gyroscope.
Microelectromechanical systems (MEMS) integrate electrical and mechanical devices on the same silicon substrate using microfabrication technologies. The electrical components are fabricated using integrated circuit processes, while the mechanical components are fabricated using micromachining processes that are compatible with the integrated circuit processes. This combination makes it possible to fabricate an entire system on a chip using standard manufacturing processes.
One common application of MEMS is the design and manufacture of sensor devices. The mechanical portion of the device provides the sensing capability, while the electrical portion processes the information obtained by the mechanical portion. One example of a MEMS sensor is a MEMS gyroscope.
A type of MEMS gyroscope uses a vibrating element to sense angular rate through the detection of a Coriolis acceleration. The vibrating element is put into oscillatory motion in the X-axis (drive plane), which is parallel to the substrate. Once the vibrating element is put in motion, it is capable of detecting angular rates induced by the substrate being rotated about the Z-axis (input plane), which is perpendicular to the substrate. The Coriolis acceleration occurs in the Y-axis (sense plane), which is perpendicular to both the X-axis and the Z-axis. The Coriolis acceleration produces a Coriolis motion that has an amplitude that is proportional to the angular rate of the substrate.
The start time of a device is the time required to produce a usable output after power application. The start time is dependant upon the cumulative times of multiple steps required to start the device. The time it takes for the drive electronics to detect and amplify the oscillatory motion of the vibrating element impacts the start time of the MEMS gyroscope.
A typical MEMS gyroscope takes between one and two seconds to start. There are MEMS gyroscope applications that require faster start times. For example, some inertial measurement units (IMUs) that include one or more MEMS gyroscopes may require a start time of one second or less.
Therefore, it would be desirable to have a MEMS gyroscope that starts in one second or less. The start time of the MEMS gyroscope is improved by reducing the time it takes for the drive electronics to detect and amplify the oscillatory motion of the vibrating element.
A MEMS gyroscope system and method for improving the start time of a MEMS gyroscope are provided. By using a noise source to inject noise into drive electronics, the start time of a MEMS gyroscope may be improved.